half of leaf missing????

hey all.... checked on my clones today... well.. they are in veg now but still in my aero/dwc cloner. anyways, checked on them today and half of 2 leaves are missing... and i cant find the remains of it anywhere... maybe bugs of some sort??? just kind of weird how it is missing and is split right down the middle. also a couple of the leaves have a few brown spots in the middle of the leaves.. i dont get it.. the other 7 clones are doin fine.... but the biggest healthiest looking one is giving me this problem.... a few of the other plants leaves wer curling up a bit but i think they are starting to go back down.

something is up here and i cant put my finger on it.... anyone care to throw in their thoughts??? maybe lack of oxygen to my roots??? i have a 12" air stone in there

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-the clones were cut about 4 weeks ago and have been in vegging for about 2 of those weeks
-under floros 24 hours a day
-ph at 5.7
-ppm @ about 250
-room temp about 73
-water temp about 75
- roots are looking healthy
- no growing medium... just netpots and neoprene collars
-sitting in aero/dwc cloner that i built myself

ps. i just added nutes the res just over a week ago and ppm was sitting at about @350 for a couple days, which was a litttle bit high for the babies so i dropped it back down to about 200-250 and has been sitting there for about a week now so the nute burn along the edges are from last week i am pretty sure.

its all in the genetics because its a clone its lost some genetics.
bud will grow the same i got same problem because of clone a clone to many times.
check it out